This study will begin with a 4-week run-in period to standardize participants' asthma medication usage. During this time, all participants will stop their current asthma medications and instead will receive inhaled fluticasone twice a day. Albuterol will be available as a rescue medication if necessary. Study visits will take place every 2 weeks. Blood and saliva samples will be obtained for laboratory tests and participants will complete standardized questionnaires to assess asthma symptoms and quality of life. Spirometry will be performed to measure lung function. Medication adherence will be monitored with a daily diary and an electronic pill counting device. At the end of Week 4, participants will be evaluated for study eligibility. If eligible, participants will undergo a bronchoscopy and a lung biopsy to test for Mycoplasma pneumoniae and Chlamydia pneumoniae, two bacteria that have been identified as possible factors in the development of asthma.